"Don't put it off because in the short term it is going to be unpopular."

Mr Clarke denied the Chancellor is "crossing his fingers", arguing that shaking up the system now is "a judgement".

He added: "I actually share George Osborne's view that this is essential if our children and our grandchildren are going to live in a successful, modern economy that is rebalanced and able to compete in the totally new world that we are beginning to face.

"If we are wrong then of course we will have to pay the price because it won't work. But meanwhile, get on with it.

"Stop looking at opinion polls and listening to the more nervous backbenchers. It is bold but I think it is necessary."

Fears: Boris Johnson said people on low incomes should be protected (Image: Christopher Furlong)